# Versioning

> How circuly API versions work and which one to use.

Every request path starts with an API version:

```http
GET https://api.circuly.io/2026-04/...
```

## Available versions

| Version    | Status   | Supported until | Notes                                            |
| ---------- | -------- | --------------- | ------------------------------------------------ |
| `2026-04`  | Current  | 1 Apr 2027      | Initial stable release. `v1` is an alias for it. |
| `unstable` | Unstable | —               | Latest unreleased changes; may change any time.  |

Versions are dated (`YYYY-MM`) and released quarterly. Each is supported for 12 months, with a 9-month overlap so you have time to migrate.

## Response headers

Every versioned response tells you what you got:

- `X-Api-Version`: the version that handled the request.
- `Sunset`: when that version stops being supported.
- `Deprecation` and `X-Api-Deprecation-Warning`: sent when the version is deprecated.
- `X-Api-Version-Warning`: sent when a sunset or unknown version was requested and the API fell forward to a supported one.

## Explore the endpoints

Pick a version in the [API reference](https://docs.development.circuly.io/api) to see its endpoints and changes.